The veteran ran the usually solid Italian champions ragged throughout the game and capped the display with a pinpoint pass to Messi for the Argentine's second goal, Barca's third, earning him a warm reception when he was substituted late on.

Lionel Messi's hat-trick against Espanyol took his tally for the season to six, while Luis Suarez is also fully fit after missing the start of the campaign with an ankle injury. "He and Neymar are the future once (Lionel) Messi and (Cristiano) Ronaldo hang up their boots", Allegri was quoted as saying by Juventus' website on Saturday.

Manchester United stamped themselves at the top of Group A with a 3 - 0 victory over FC Basel. Given the current situation of the team, Mattia De Sciglio, Daniele Rugani, Medhi Benatia and Kwadwo Asamoah are expected to form the back line.

Sami Khedira is a doubt for their trip to Spain and without the former Real Madrid man, the likes of Blaise Matuidi and Mirajlem Pjanic will have to pick up the slack in the middle of the pitch.

However, this is a much-changed Bianconeri that we are witnessing this season.

Barcelona made a lot of headlines over the summer, mostly for the wrong reasons.

The Catalonians were extremely convincing, and they smashed the Italian champion completely avenging the brutal beating in last year's quarter-finals. In the past five meets between Barcelona and Juventus, Juventus won two matches, Barcelona won two matches and the other match ended in ad draw.

And for most of the first half of Barcelona's opening Champions League group match against Juventus, it was Messi trying to create to no avail. In order to do that, we need to be signing quality players.

Perhaps the Italy international's departure from Turin shall also see the death of the three-at-the-back system in the Piedmont capital, with Allegri preferring a 4-2-3-1 now.

This will be Barcelona's 22nd appearance in the competition, which matches Real Madrid and Porto for the most all-time, and their 14th consecutive appearance - second only to Real Madrid. "It is a good win for confidence".

Barcelona have topped their group in each Champions League campaign since the 2007-08 season.